1. Field of the Invention
The present invention relates generally to laser systems and more particularly to directional optical isolators.
2. Description Of The Related Art
It is frequently necessary to isolate from a desired laser beam an unwanted laser beam characterized by a frequency similar to the frequency of the desired beam but propagating in a direction opposite to the direction of the desired beam. For example, under certain conditions a laser beam that propagates around a ring oscillator in the wrong direction can interfere with proper operation of the oscillator, and it is therefore necessary to isolate and thereby suppress such a backwardly propagating beam without interfering with a beam propagating forwardly around the ring.
Isolation of an unwanted, backwardly propagating laser beam can sometimes be achieved by means of a magneto-optic isolator (also known as a Faraday isolator). Such isolators are used, for example, to control parasitic laser feedback. However, magnetooptic isolators are characterized by relatively slow switching speeds and hence are not suitable for use in devices requiring reversible isolators which can be switched rapidly back and forth between isolating a laser beam propagating in one direction and isolating a beam propagating in an opposite direction. In addition, magneto-optic isolators are relatively inconvenient because they often require powerful magnetic fields and large electromagnets.
Accordingly, there is a need for an optical isolator which can be rapidly switched from isolating a laser beam propagating in one direction to isolating a beam propagating in the other direction and which does not need bulky magnets in order to function properly.